Which type of fire alarm circuit does NOT include redundancy?

Class B fire alarm circuits are characterized by their straightforward design, where each device is wired in a single continuous loop to the control panel. This setup means that if a break occurs in the circuit, all devices located beyond the break will stop functioning, and the points of detection may be compromised. The absence of redundant pathways or additional connections in Class B circuits leads to vulnerability; if one device fails or the circuit is interrupted, it can affect the entire operation of the detection system.

In contrast, Class A circuits are designed with redundancy, allowing for alternate pathways for the flow of current. This increased resilience means that devices can remain operational even if a fault occurs in one part of the circuit. Class C and Class D circuits also typically involve increased complexity and redundancy compared to Class B. This lack of redundancy in Class B circuits is why this option stands out in the context of the question.